Wireless telecommunications systems of the prior art typically employ a separate high power radio frequency (RF) amplifier to excite each transmitting antenna used at the base station. Typically, each power amplifier amplifies modulated RF signals of a plurality of frequency channels for transmission to mobile users and/or to stationary sites. Multi-sector systems employ a plurality of directional antennas to provide directional beams over predefined azimuthal sectors, thereby attaining 360 degree coverage with improved range. Each power amplifier associated with a given antenna is thus dedicated to amplifying only those signals to be transmitted within the associated azimuthal sector.
FIG. 1 depicts a schematic block diagram of a prior art base station transmitter configuration for a three sector system. Antennas AT.sub.1 -AT.sub.3 each transceive within a given 120.degree. azimuthal sector to achieve 360.degree. coverage within a given radius of the base station. Power amplifiers P.sub.1 -P.sub.3 each amplify a respective multiplexer signal S.sub.MUX1 -S.sub.MUX3, which are typically frequency division multiplexed (FDM) signals. N-channel combiners CN.sub.1 -CN.sub.3 each combine up to N input signals to provide the multiplexed signals. Power amplifiers P.sub.1 -P.sub.3 are generally sized so as to handle a peak traffic load that is based on statistics or on the maximum number of radios in its associated sector, since traffic load fluctuates minute by minute.
When a large number of users are communicating from a single azimuthal sector, the power amplifier P.sub.1 -P.sub.3 associated with that sector is fully utilized, while the other power amplifiers, which service other azimuthal sectors, may be under-utilized. Accordingly, RF power is not efficiently distributed in the system of FIG. 1. One solution to this inefficient power distribution is described in my copending U.S. patent application Ser. No. 08/542,480, filed Oct. 13, 1995, and assigned to the assignee herein. Therein, a power sharing amplifier network is described, which includes a plurality of amplifiers in a power sharing arrangement, such that each amplifier amplifies an approximately equal amount of RF power. Each amplifier in the network amplifies a composite signal containing signal power from all the communication signals to be transmitted by the system. In this manner, average power is efficiently shared between the amplifiers, such that the system can accommodate a larger number of subscribers. Further, feed-forward loops are employed to reduce distortion within the output signals.
While the amplifiers in the amplifier network described in the above-cited patent application share average RF power, instantaneous peak power differs between the amplifiers due to the varying phase relationships between the multi-carrier components of the signals applied to the amplifiers. Due to the random phase of the input signals, peak power can periodically peak to undesirable extremes in any given amplifier. The amplifiers must therefore be designed to handle such peak power, resulting in an increase in amplifier cost and complexity. Accordingly, there is a need to reduce instantaneous peak power applied to the amplifiers of a power sharing amplifier network.